THE BEHAVIOR OF CERTAIN MICRO-ORGANISMS IN BRINE. 



51 



The next point to establish is the average temperatures. The mean annual tempera- 

 ture is not far from 58° F., with the lowest monthly mean in January and the highest 

 in July. The daily range is regularly greater than the seasonal range, the difference 

 between the average daily maximum and average daily minimum being greater than the 

 difference between the mean temperatures of the coldest and the warmest months of the 

 year. The season of greatest warmth is that of least rainfall, and vice versa. The average 

 of the maximum temperatures in July for 23 years at Menlo Park, 4 miles from the Red- 

 wood salt ponds and on the valley floor, is 92.7° F. The average of the minimum temper- 

 atures in December, for the same 23 years, is 30.4°. 



In the evaporation of any solution there are concerned the degree of concentration 

 and the composition of the solution, its temperature and that of the surrounding medium, 

 the proportions of the evaporating solvent in the surrounding medium, the frequency, 

 quantities, and compositions of the materials which may be added to it. Rain-water is 

 usually added to whatever may be in the brine ponds at Redwood City only during the 

 cool months of the year, or when evaporation is slow because of the prevailing low tem- 

 peratures. The air-temperatures will necessarily influence the temperature of the brines. 

 We see that the air is warmest when the days are longest. The records given below (table 22, 

 pp. 56-60) suggest also the degree to which the temperature of the air influences the temper- 

 ature of the brine. But the rate at which a brine will concentrate will depend also upon the 

 humidity of the air. This is given in the Annual Reports of the Chief of the Weather Bureau, 

 for the cities of San Francisco and San Jose, but not for Redwood. The San Francisco figures 

 are of little value, since it lies in the path of the summer fogs which constitute such a 

 marked and beneficial feature of the coast climate of middle California; and the San Jose 

 figures are incomplete, being reported only for 8 p.m. 1 The time of lowest humidity and of 

 most rapid evaporation would generally be that of highest temperatures. This is patent to 

 anyone so far as daily conditions go, but people accustomed to the humid summers of the 

 eastern and central States and of middle and western Europe do not realize that on the 

 Pacific Coast conditions are opposite to those to the eastward. Thus our season of greatest 

 humidity, outside of the coast "fog belt," is the winter rainy season with its moderately low 

 temperatures, whereas the rainless summer, with moderately high mid-day temperatures, has 

 low humidity. The condition may be illustrated by comparing the data for Cincinnati and 

 St. Louis with those for San Jose, comparing a moist fertile region with one semi-arid. Thus 

 the mean temperatures and humidity at 8 p.m. in June, July, August, and September, 1910, 

 in Cincinnati, Ohio, were 76.95° F. and 58.5 per cent; in St. Louis, Missouri, 77.45° F. and 

 62.7 per cent; in San Jose 72.50° F. and 54 per cent. 



Turning from this to the cloudiness and clearness as indicating the conditions which 

 affect evaporation and the rate of concentration of the brines, we find reports of the follow- 

 ing fractions by the Chief of the Weather Bureau for 1910 (table 21) : 



Table 21. 



These figures again have less value than I should like, for the records on which they 

 are based are made at the end and not in the middle of the day. The percentage of cloudi- 



1 8 p.m. Washington equals 5 p.m. on the Pacific Coast, U. S. Standard time. 



